Tashkeel mistake, should be غالِية
Yes it is
What makes حقيبة different from شنطة?
Apparently, haqeeba is the more standard word while shanTa is dialectic.
How would you say "a bag is expensive"? and why wouldn't it look like this?
In Arabic you cannot have the subject indefinite unless you specify it further. e.g. حقيبة من الحقائب غالية